Electrical generating system



June 9,- 1931.

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ELECTRICAL GENERAT'NG SYSTEM Filed Feb. 15, 1929 IN V EN TOR.

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Patented. June 9, `1931 UNITED STATI-:s` PATENT OFFICE CHARLES A. CULVEB, OF NORTHFIELD, MINNESOTA, ASSIGNOR TO WIRED RADIO, INC., OF NEW' YORK, N. Y., .A CORPORATION OF DELAWARE ELEUIRIQAL GENERATING SYSTEM My invention relates to electrical energy generating systems in general and more frequency electrical energy employed in sig- Q5? naling systems. v

An object of my invention 1s to. provide a system for the conversion of variable light energy into alternating current. i

Another object of my invention 1s to pro- .l0 vide a system for the transformation of variable incident light into electrical energy havin a definite frequency.

till another obj-ect of my invention is to provide a system for the transformation of l5 variable incident light energy into electrlcal energy having a relatively high frequency.

ln the transmission of pictures over physical circuits and also by means of electromagnetic Waves traveling through space, it au is primarily necessary to provide some means for first converting the light energy from the picture into electrical energy. Variations in the intensity of the -light energy, corresponding to relatively light and dark portions ol'the picture, cause variations in the amplitude of the transmitted electrical energy. it the receiving station these variations in the amplitude of electrical energy are converted bach to variations of light energy. The accurate and complete conversion oivariations of light energy into variations of electrical energy is accomplished'in the electrical generatin system of my invention, a better understan ing of which can be had from the specication following and from the accompanying drawing which is, a schematic circuit diagram showing one form of my invention.

lhe photoelectriocell is employed in systems for the conversion of variable light energy into electrical energy and usually comprises a container or envelope l of glass or suitable silicate composition having a cathode 2 and an anode 3 sealed within. Cathode 2 is coated with a light sensitive material such as potassium, barium or other material capable of emitting electrons proportional to light intensity. An anode 3 is spacially positioned adjacent the cathode 2 within envelope 1 in such a manner as to be Application led February 15, 1929. Serial No. 340,206.

a target. for the electrons emitted from cathode 2. Should a source of electrical energy and a meter be connected across these tvvo electrodes a current would be found to exist, which current is inversely proportional to the resistance between the electrodes or directly proportional to the light energy incident upon the cathode.

In the electrical generating system of my n invention a control electrode 6 which resembles a grid, is spacially positioned in the path of the electronic stream between cathode 2 and anode-3. rlhe potential supplied control electrode 6 has amarked influence on the number of electrons reaching anode?) and hence upon the resistance of the tube. When a difference of potential is supplied between anode 3 and cathode 2 in such a manner as to supply the anode 3 with a positive polarity and cathode 2 with a corresponding negative polarity, electrons liberated from cathode 2 will travel toward anode 3. Such a source l2 is connected in series with cathode 2 and high frequency choke coil i3 to anode 3. A source of biasing fpotential is supplied to control electrode 6 rom source ll connected in series with cathode 2 and high frequency choke coil l5. Anode 3 is associated with one end of inductance 7 by means of condenser ll. Control electrode 6 is associated with the opposite end of inductance 7. Condensers 9 and l() are connected in series and the series connected in parallel with inductance 75 the connection betWen the two condensers being connected to cathode 2.1 Condenser 9 is of the adjustable capacity design, as may also be condenser 10, but an adjustable capacity may not be necessary. A. load circuit@ may be associated with inductance 7, either inductively as illustrated or by suitable capacity cou ling. A lens 5 is positioned adjacent to ano e 3 in such a manner as to cause light rays incident thereon to converge to the aperture d provided in anode 3. From aperture e the rays are caused to diverge over the surface of cathode 2. The surface of cathode 2 being coated with light sensitive material, the rays of li ht falling thereon cause photoelectrons to e emitted. The photoelectrons thus emitted are attracted to anode 3 because of the potential dierence kco and positive polarity of anode 3. If control electrode 6 has a negative polarity' with respect to cathode 2 the passage of the electrons across the space between the cathode 2 and anode 3 will be retarded. If, however, control electrode 6 has al positive polarity with respect to cathode 2` the passage of the electrons will be positively accelerated.

In the respect last mentioned the photoelectric cell functions very much in a manner similar to that of the three electrode thermionic tube. Any variation of the potential supplied control electrode 6 will result in a corresponding variation of the current in the anode circuit. Since the cathode and anode circuits are electrostatically coupled, any variations of the current in the cathode-anode circuit will develop a corresponding potential variation in the cathode-control electrode circuit.

The input and output circuits 'may be electromagnetically coupled instead of electrostatically coupled, and in either case the interaction effects the generation of electromagnetic oscillations in a manner well known to those skilled in the art. The frequency of the generated oscillations depends upon the capacity of the condensers 9 and 10 and the inductance value of inductance 7. Ca acity ll, does in a measure, contribute to the requency characteristics of the circuit arrangement as does also the internal capacity of electrodes 2, 3 and 6 of the photoelectric cell. For a constant source of light energy and hence a constant source of photo-excitation the maximum amplitude of the high frequency oscillating energy will be determined by the potential of source 12, the design of the cell and the inherent losses in the circuit. If, however, the source of light is variable in intensity, the amplitude of the high frequency alternating current generated, will be a function of the intensity of the incident light. The high frequency energy may be amplified by means of thermionic tube amplifier circuits associated with inductance 8. Such amplified high freruency energy may be radiated by a s ace ra io system or be transmitted over p ysical circuits. The generating system of m invention may be employed for the transmission of pictures, moving pictures, scenes or the like.

' I realize that many modifications of my invention are possible and it is to be understood that the embodiments of my invention are not to be limited by the fore oing specifcation or by the accompanying rawlng but onl by the scope of the appended claims.

at I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An electric vgenerating system comprising in combination a source of light energy, a photoelectric cell having a light sensitive electron emitting cathode energizable by said intensity of the light energy incident thereon.

`2. A high frequency generating system comprising in combination a photoelectric cell having a light sensitive cathode, an anode and control electrode, input and output circuits connected to said cathode, anode and control electrode for establishing high frequency oscillations, and a source of light energy incident upon said cathode for modulating said high frequency oscillations.

3. A generator of high frequency electrical oscillations comprising in combination a three electrode photoelectric cell having electrically coupled input and output circuits, said input and output circuits having substantially like frequency characteristics for sustaining electrical oscillations, the cathode of said photoelectric cell having light sensitive electron emitting properties and a source of light directed upon said cathode and adapted to energize the same for varying the impedance of said photoelectric cell and correspondingly controlling the amplitude of the electrical oscillations.

4. An alternating current generating system comprising in combination a photoelectric cell having a light sensitive electron emitting cathod, anode and control electrode, an input circuit comprising inductance and capacitance connected with said cathode and control electrode, an output circuit comprising inductance and capacitance connected with said anode and cathode and a source of variable luminous energy incident upon said cathode for changing the internal impedance of said photoelectric cell and correspondingly controlling the amplitude of the alternating current.

5. A high frequency generating syste comprising in combination a photoelectric cell having a light sensitive electron emitting cathode, anode and control electrode, an input circuit comprising inductance and capacity connected with said cathode and control electrode. an output circuit comprising inductance and capacity connected with said anode and cathode, said inputand output circuits being coupled for generating sustained high frequency oscillations, and a source of variable luminous energy directed upon said cathode for chan ing the impedance of said photoelectric cel and modulating the oscillations sustained in said circuits.

In testimony whereof I affix my signature.

` .CHARLES A. CULVER. 

